Alzheimer's disease (AD), the sixth leading cause of death in the United States, currently affects over 5 million North Americans and their families as well as the United States health care system. Impaired olfactory perceptual acuity, including deficits in odor identification, detection and discrimination are often observed early in the progression of AD. Understanding the neural basis for these sensory deficits is important in that 1) their etiology may unveil new insights into AD pathogenesis and 2) olfactory screens may serve as early-indicators of AD when combined with neuropsychological examinations. SPECIFIC AIMS: This proposal describes an experimental strategy aimed at understanding the contributions of amyloid-2 (A2) to olfactory system dysfunction. Behavioral, neurophysiological and molecular experiments will be performed in mice which overexpress human mutations of Amyloid 2 Precursor Protein (APP). Aim 1 will test the hypothesis that progressive A2 burden and AD-like olfactory perceptual deficits are related to abnormal odor information processing at local and global levels in AP transgenic mice. The remaining two aims will utilize novel genetic models of A2 remediation to examine methods to rescue/preserve olfactory function in APP transgenics. AIM 2 wil test the hypothesis that chronic enhancement of A2 degradation improves olfactory processing and perception by using mice which lack the protease inhibitor cystatin B (CBKO). AIM 3 will use mice over expressing the protease inhibitor cystatin C (CysC) to test the hypothesis that preventing A2 aggregation improves olfactory procesing and perception. These ongoing studies are the first to directly assess the contributions of A2 to olfactory perceptual dysfunction.